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Clinical applications of magnesium (Mg)-based screws have reported gas cavity formation in the surrounding tissue, which sometimes delays the fixation of the bone fracture. The gas cavity formation is considered to depend on the balance between hydrogen generation by Mg corrosion reacting with water in the body fluid and its diffusion into the surrounding tissue by capillary flow. In order to understand the gas cavity formation behavior by Mg-based material implantation, we developed a new in vitro model system to recreate this cavity formation phenomenon: the hydrogen generation by corrosion and its diffusion into the medium. A model tissue is prepared by gelation of the cell culture medium in a sterile condition. The immersion of Mg alloy samples was performed under 5% CO2 atmosphere with periodic observation by X-ray computed tomography, which enabled us to observe gas cavity growth up to 28 d. For demonstrating the usefulness of our model system, Mg alloy samples with different corrosion rates were prepared by a biodegradable polymer coating. AZ31 screws were spin-coated by poly-L-lactide (PLLA) and classified into three groups by their coating thickness as 1.0 ± 0.0, 1.6 ± 0.2, and 2.0 ± 0.1 μm (ave. ± s.d.). Upon their immersion into the model tissue, the gas cavity volumes formed were 1.57 ± 0.23, 1.06 ± 0.22, and 0.38 ± 0.09 mm3/mm2 for 1.0, 1.6, and 2.0 μm coating samples, having the weight loss of 20.2 ± 2.93, 18.5 ± 2.84, and 11.3 ± 3.54 μg/mm2, respectively (ave. ± s.d.). This result clearly indicates the dependence of gas cavity formation on the corrosion rate of the sample. The gas cavity volume was only 3.3∼7.5% of the total hydrogen gas volume estimated based on the weight loss of the samples at 28 d, which is in the range of those calculated
from the clinical report (3.2∼9.4% at 4w). This system can be an effective tool to investigate the gas cavity formation behavior and contribute to understand the mechanisms and controlling factors of this phenomenon.

権利情報:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

キーワード: biodegradable metals, magnesium alloys, biocorrosion, hydrogen gas, in vitro evaluation

刊行年月日: 2022-06-13

出版者: American Chemical Society (ACS)

掲載誌:

• ACS Biomaterials Science & Engineering (ISSN: 23739878) vol. 8 issue. 6 p. 2437-2444

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1021/acsbiomaterials.1c01429

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更新時刻: 2024-01-25 09:50:26 +0900

MDRでの公開時刻: 2024-01-25 12:30:14 +0900